The present invention relates to tools used in the in the oil and gas drilling industry to grip and rotate tubular members such as drill pipe. More particularly, the present invention relates to the jaw assembly, which is the component of such tools actually coming into contact with the tubular.
In the oil and gas drilling industry, a certain class of machines known as power tongs are employed to grip and rotate drill pipe and other tubular members in the process of making up or breaking apart the joints on a string of tubulars. Typically, when a tubular joint is be made up or broken apart, back-up power tongs will grip the tubular on one side of the joint and power tongs will grip the tubular on the opposite side of the joint. The power tongs are used to apply torque to one tubular while the back-up power tongs (hereinafter referred to simply as "back-up tongs") are used to hold the other tubular stationary against rotation. Both the back-up tongs and the power tongs must have a means to securely grip the tubular when large torque loads are being applied. One such gripping means is a jaw member having a concave shaped die insert such as seen in U.S. Pat. No. 4,576,067 to Buck. The die insert may have a knurled surface in order to better grip the tubular. However, the die must be easily replaceable in the jaw member because the knurled surface is eventually worn smooth during use and loses its gripping characteristics. While being replaceable, the dies must also be able to transfer large torque loads between the jaw member and the tubular without the die breaking its mounting in the jaw member. One successful solution to this problem is disclosed in U.S. Pat. No. 4,576,067 to Buck where the jaw member and die have a plurality splines and grooves that interlock lock the jaw member and die together.
However, the torque load imparting a force transverse to the splines and grooves is not the only force acting on the die. In certain situations, a vertical force parallel to the spline and grooves is exerted on the dies. To resist this vertical force, the prior art typically employed some type of retaining screw. If the vertical force becomes great enough, the retaining screw fails and the die is displaced from the jaw. What is needed in the art is an improved method of making the die secure in the jaw member from vertical displacement.